Photographic diffusion transfer product and process

ABSTRACT

A RECEIVING SHEET FOR USE IN A DIFFUSION TRANSFER PROCESS COMPRISES A POLYOLEFIN SURFACE SUCH AS POLYETHYLENE OVER WHICH IS COATED A CELLULOSE ESTER LAYER SUCH AS CELLULOSE TRIACETATE AND OVER WHICH IS THEN COATED AN IMAGE RECEIVING LAYER. THE IMAGE RECEIVING LAYER CAN BE A NUCLEATED   LAYER FOR USE IN BLACK AND WHITE DIFFUSION TRANSFER OR A MORDANTED LAYER FOR USE IN COLOR DIFFUSION TRANSFER.

July 17, 1973 Filed Nov.

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T. F. PARSONS 3,746,564

GEL/lT/IV IVUCLE/ L A YER P- GEL A T/N- CEL L ULOSE N/TRA TE SUBCELLULOSE TR/ACETATE-l-BR/GHTENER GELAT/N- CELLULOSE lV/TRATE SUB 5\\\k-a EAR POL YE TH YL ENE "V/// F/GI 2 BARYTA APER STOCK \%wH/rE POLYETHYLENE /0 'E\\ B "V/ GELATl/V MORDA/VTED LAYER -6ELAT//VCELLULO$EN/TRATE SUB CELLULOSE TR/ACETATE l-BR/GHTENER GEL KIT/N CELLULOSE N/ TEATE SUB m-CLEAR POLYETHYLE/VE &

/ }-EARYTA PAPER STOCK BLACK POLYETHYLENE "WH/TE POLYETHYLE/VE TIMOTHY FPARSONS INVENTOR.

ATTORNEY United States Patent 3,746,564 PHOTOGRAPHIC DIFFUSION TRANSFERPRODUCT AND PROCESS Timothy F. Parsons, Hilton, N. assignor to EastmanKodak Company, Rochester, NY. Filed Nov. 19, 1970, Ser. No. 91,042

Int. Cl. B05c 9/04 US. Cl. 117-68 7 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION This invention concerns receiving sheets foruse in a diffusion transfer process. More particularly, it concernsreceiving sheets having improved abrasion resistance and improvedadhesion of image receiving layers.

Diffusion transfer processes are well known. For example, IRott US. Pat.2,352,014 describes such a process wherein undeveloped silver halide ofan exposed photographic emulsion layer is transferred as a silvercomplex imagewise by imbibition to a silver precipitating or nucleatinglayer, generally to form a positive image therein. A silverprecipitating or nucleating layer generally comprises a bindercontaining nuclei such as nickel sulfide, colloidal metal or the like.

In a conventional black and white diffusion transfer process, aprocessing solution containing a silver halide developer, a silverhalide solvent and as viscous filmforming agent having a relatively highpH is employed. An element is processed by squeezing the viscousprocessing material between the exposed silver halide emulsion and thereceiving sheet. The receiving sheet is then separated from the silverhalide emulsion layer and the receiving sheet contains the desiredprint.

Photographic color diffusion transfer processes utilizing dye imagereceiving elements are also well known as is illustrated by Beavers etal. US. Patent 3,445,228 issued May 20, 1969, Bush US. Patent 3,271,147issued Sept. 6, 1966, Whitmore US. Patent 3,227,552 and Whitmore et al.US. Patent 3,227,550, issued Jan. 4, 1966.

In photographic color diffusion transfer processes, image reproductionis effected by developing an exposed silver halide emulsion layer havingassociated therewith a non-diffusible color-forming coupler that forms adiffusible dye when reacted with an oxidized color developing agent,reacting oxidized aromatic primary amino color developing agent withsuch coupler, and allowing the resulting dye to diffuse to a receptionlayer for such dyes. A color diffusion transfer system typically employsa photosensitive element comprising three differentially spectrallysensitized silver halide emulsion layers, each of which layers havingassociated therewith a nondiffnsible coupler compound capable ofyielding the appropriate diffusible complementary color dye upondevelopment with oxidized aromatic primary amino color developing agent.

The reception layer is typically a mordanted layer on a suitablesupport. The transfer of the color dye images to the reception layer isaccompanied by small amounts of development reaction products and unusedcolor developing agent. Such materials transferred with the dye image tothe reception element are objectionable because of the tendency of thesetransfer materials to form stain,

3,746,564 Patented July 17, 1973 "ice particularly in the highlight or Dareas. 'In a similar manner, prints obtained by the black and whitediffusion transfer process have been subjected to various problemsincluding the problem of stability with respect to the presence ofprocessing chemicals retained in the element.

Therefore, it has been desirable to employ a paper support having apolymeric coating thereon such as a polyolefin coating, in particularpolyethylene, which reduces the penetration of these developmentreaction products and the like into the paper support, thereby reducingstain and improving the stability of the dye image. However, the use ofpolyethylene coated paper has resulted in problems such as pooradhesion, low abrasion resistance, and the like. Electron bombardment ofpolyethylene surfaces or similar treatments have been conventionallyused in order to improve the adhesion of coatings thereon, but the useof electron bombardment or similar treatments by themselves have notresulted in satisfactory resistance to abrasion even though adhesion isgood.

SUMMARY OF THE INVENTION In accordance with this invention it has beenfound that a receiving element for use in a black and white or colordiffusion transfer process comprises a polyolefin surface such aspolyethylene having thereon a cellulose ester layer over which is coatedan image receiving layer. It will be appreciated that other layers maybe interposed between the cellulose ester layer and the receiving layeror that subbing layers may be employed in order to still further improveadhesion of these layers.

In a preferred embodiment for use in a silver diffusion transferprocess, a polyethylene surface is electron bombarded to improveadhesion and coated with a gelatincellulose nitrate subbing. A layer ofcellulose triacetate containing a brightener is then coated over thepolyethylene and on this layer of cellulose triacetate is coated agelatin-cellulose nitrate subbing and a gelatin layer containing silverprecipitating nuclei such as palladium metal. In a preferred embodimentfor use in color diffusion transfer, and employing a similar structure,a gelatin mordanted receiving layer is used instead of a silverprecipitating layer.

A receiving element as described above is used advantageously to providea photographic print having an image in a receiving layer on a supportby the photographic silver salt diffusion transfer process or colordiffusion transfer process.

DESCRIPTION OF PREFERRED EMBODIMENTS If a support is employed, paper ispreferred and can be any of the conventional cellulose supportsincluding those prepared from cotton, linen, and Wood (sulfate andsulfite pulped) and which supports are typically about 5-60 pounds per1000 square foot papers.

The polymeric material which forms the surface for the receiving sheetof this invention can be coated over any support, typically in athickness of about .3 to 5 mils. For instance, particularly usefulmaterials include the polyolefins prepared from the alpa-olefins having2-10 carbon atoms and blends of these polyolefins as well as copolymers.The coatings may be applied by extrusion or hot melt coating techniquesas latexes, as solvent coatings, etc. If the polyolefin isself-supporting, it can be of any thickness.

In some instances it is desirable to incorporate in the polymericmaterial at least one pigment or dye, especially where a whitebackground is required, but this is not required. In a particularlyuseful embodiment, titanium dioxide is incorporated as a pigment in anamount of up to 25%, preferably 10-15% by weight of the resin. Otherpigments or dyes which may be useful include those commonly knownpigments or dyes for polymeric materials.

The polyolefin surface can be given an additional treatment when thepolyolefin material such as polyethylene is extruded but this is notnecessary to this invention. Shortly after extrusion, the polymericmaterial is contacted against a chilled roll which may be glossy,preferably, or matte depending upon the desired finish. In anotherembodiment, the coating is placed on the support as a latex or solventcoating and then contacted against a hot glossy roll in order to providea glossy or matte finish. This is particularly suitable when a latexcoating has been applied or when the polymeric surface has been softenedon the surface by contacting with a semisolvent solution which softensthe surface of the coating. In still another embodiment a latex coatingmay be applied to a support after which the coated support is subjectedto heat such as by hot air impinging on the surface or from infraredlamps directed to the surface.

The polymeric surface is then given a treatment to improve thehydrophilic character of the surface to improve adhesion. Typicaltreatments which are particularly suitable for use with hydrophobicpolyolefin polymers, such as polyethylene, include treatments with aflame, use of an oxidizing agent such as nitric acid, sodiumhypochlorate, chlorine, hydrogen peroxide, sulfuric acid and potassiumchromate, etc., electron bombardment, radiation by ultraviolet light,etc.

Electron bombardment of polymeric surfaces is conveniently carried outby means of a corona discharge. Variations in electrical conditions maybe used with re spect to frequency, voltage, number of electrodes,spacing between the discharge gap, medium used in the discharge gap,such as an inert gas, ozone, etc. Apparatus disclosed in Rothackerpatents, U.S. 2,864,755 and 2,864,- 756, can be utilized. The level ofelectron bombardment or similar surface treatment of the polymericsurface can be measured by the contact angle obtained when a drop ofdistilled water is placed on a level sample of the polymeric coating. Byprojecting the image of the drop and sample on a suitable screen, andmeasuring the angle of a line tangent to the drop image at the pointwhere the drop touches the polymeric sample, a contact angle is obtainedwhich can be measured and utilized to determine the degree ofhydrophilicity. Generally untreated polyethylene coated paper gives acontact angle of about 90". A contact angle of preferably from about 40to about 75 improves the adhesion of hydrophilic coatings and is highlydesirable for coatings such as cellulose ester coatings, subbingcoatings or the like. With polypropylene, the preferred contact angle ispreferably less than 54 for subsequent coatings.

Typical methods of treating polyethylene by electron bombardment aredisclosed in Traver U.S. Pat. 3,018,189 directed to methods fortreating. the surface of polyethylene with electrostatic discharges tochange the surface properties of the polyethylene with respect toadhesion of materials coated thereon. British patent specification715,915 issued to the Visking Corp., published Sept. 22, 1954 alsodiscloses a method and apparatus for treating plastic structures with acorona discharge.

Another method of improving the adhesion of a cellulose ester to apolyolefin coated surface is illustrated by Alsup U.S. Pat. 3,161,519,issued Dec. 15, 1964, in which colloidal silica is employed in a coatingover the polyolefin surface. In the particular disclosure therein, acoating mixture containing colloidal silica is coated on untreatedpolyethylene coated paper and dried with hot air at about 150 F. Aparticular useful coating composition is disclosed in Example 6 in whichan acrylic resin is employed in the coating composition.

In any event, the use of the coating of cellulose ester over thepolyolefin coated surface improves the abrasion resistance regardless ofwhether the polyolefin has re- 4 ceived an additional treatment toimprove its adhesion.

It will be appreciated that various layers of polymer may be coated on asupport such as paper. For instance, in order to obtain opacity, a layerof polyethylene pigmented black can be coated on the back of the papercovered by a layer of polyethylene pigmented white. On the face side ofthe paper, it is sometimes desirable to coat a layer of baryta plus adye or brightener over which can be coated a layer of clear polyethyleneplus a pigment such as titanium dioxide. However, in order to obtain theadvantages of the invention, a layer of cellulose ester is coated overthe polyolefin either with or without a subbing applied between thepolyolefin surface and the cellulose ester layer. Over the celluloseester layer can be coated a receiving layer with or without a subbinglayer. If a subbing layer is used, it can be of the type describedherein as useful between the polyolefin layer and the cellulose esterlayer.

Cellulose esters which can be coated over the polyolefin layer includethose which are obtained from organic acids having 24 carbon atomsincluding mixed esters such as cellulose acetate butyratc, celluloseacetate propionate and the like. Particularly useful esters are those oflower aliphatic, preferably monocarboxylic acids, such as celluloseacetate, cellulose triacetate, cellulose butyrate and the like. Typicalcellulose ester formulations are described in Fordyce et al. U.S. Pats.2,492,977 and 2,492,- 978 issued Jan. 3, 1950, Fordyce et al. U.S. Pat.2,739,- 070 issued Mar. 20, 1965, and Fordyce et al. U.S. Pat. 2,607,704issued Aug. 19, 1952.

For some purposes, a subbing can be used such as a gelatin-nitratesubbing. The gelatin nitrate sub is particularly useful when coating agelatin coating on the surface of a plastic overcoat such as a celluloseester. Typical coatings are disclosed in the Nadeau et al. U.S. Pat.2,614,932 issued Oct. 21, 1952, Nadeau U.S. Pat. No. 2,133,110 issuedOct. 11, 1938. Of course, the nature of the subbing coated on thecellulose ester layer depends upon the nature of the binder used in themordanted or nucleated layer coated over the subbing. In a preferredembodiment employing gelatin in the receiving layer, it is particularlyuseful to use the gelatin-cellulose nitrate subbing such as is disclosedin the above Nadeau et al. patent.

Subbing compositions which can be used on polyethylene to adhere to thecellulose ester coating do not require any gelatin but can include awide variety of materials provided that one of the solid components issoluble in a solvent for the particular cellulose ester. Any of thesubbing compositions mentioned above can be used either admixed withgelatin or by themselves. It will be appreciated that any subbingmixture can be used having good adhesion properties including thoseknown for use in adhering silver halide emulsions to cellulose estersupports or those adhering silver halide emulsions to polyester supports, and the like. Typical coatings are described in Secrist U.S.Patents 3,212,897 issued Oct. 19, 1965 and 3,320,191 issued May 16,1967. The subbing which can be employed to improve the adhesion of thecellulose ester layer to the polyolefin surface can perform an importantfunction in the invention. It should be of sufiicient strength' andhardness and sufiiciently adherent to the adjacent surfaces to bond thecellulose ester layer firmly to the polyethylene.

A sub of gelatin-cellulose nitrate mixture within relatively narrowlimits can be used. The subbing layer, preferably contains between about0.005 and 0.020 g. of solids per square foot, equivalent to 30 to 80weight percent solids of gelatin and to 20 weight percent solids ofcellulose nitrate. The solvent used for applying the subbing layersshould comprise a miscible mixture of solids for both components,preferably a mixture of acetone, methanol and water. In a particularlyuseful embodiment of this subbing, a solution containing 25 percentcellulose nitrate and percent gelatin is coated at 0.012 g. per

square foot using an acetone-methanol water solvent. The cellulosenitrate gelatin subbing can be prepared by blending cellulose nitrateresin with gelatin using water and one or more solvents such as methylethyl ketone, acetone, ethylene dichloride, ethyleneglycolmonomethylether, etc. In another embodiment, a gelatin subbing can beemployed by preparing the subbing with water and one or more solventssuch as acetone, ethylene dichloride, ethyleneglycol monomethylether,etc. Still another subbing is made by blending a resin such as apolyacrylate, a carboxylated polyester, or a copolymer of 2-chloroethylacrylate, vinylidene chloride and acrylic acid with gelatin and suitablesolvents.

The cellulose ester can be applied as a solvent coating so that itprovides a cellulose ester layer having a thickness of about .1 to .4mil or a coverage of 2.5 g./m. to 10 g./m. The cellulose ester cancontain addenda such as a pigment or a brightener, dyes, plasticizers,etc.

The brighteners which can be incorporated in the cellulose ester coatingin any suitable concentrations, particularly good results being obtainedat concentrations at about 0.01 to about 1.0 percent by weight of awhitening or brightening agent. For example, 4-4'-bis(benzoxazo1-2-yl)stilbene compounds are especially useful. Other compounds which areuseful include the following structure and described in Belgian Patent612,775:

CH3 HC CH CH3 CH3-|C n-on:

a. M a.

\0/ S \O/ and 4,4'-bis ,7-di-t-amylbenzoxazol-Z-yl stilbene C H -t Otherwhiteners include coumarins of the type described in British Patent786,234 and fluorescent compounds of the formula:

N A1-/-CH=CH\ sk -0 A in which A is a substituted or unsubstitutedphenyl radical. A is a substituted or unsubstituted p-phenyleue radical,A is a substituted or unsubstituted arylene radical, e.g., ano-ph'enylene radical or a :1,2-naphthylene radical, in which two vicinalcarbon atoms are bonded to the oxygen and nitrogen atoms respectively ofthe oxazole ring and n is an integer from 1 to 2, as described inSaunders US. application Ser. No. 229,162 filed Aug. 1, 1963, nowabandoned. Another useful brightener is3-(p-chlorophenyl)-7-(2[dimethylaminoethyl] ureido)coumarin, Tinopal SFG(Geigy), having the formula:

The plasticizing agents can be omitted, but if desired, any of thosetypically used in cellulose esters can be employed.

In one embodiment for the color diffusion transfer element, a mordant isused in a gelatin layer as the receiving layer in the photographicelement described herein. Any satisfactory mordant may be used. However,particularly useful mordants are those disclosed in Bush US. Patent No.3,271,147, and Cohen et al. Belgian Patent No. 729,202.

Mordanting and thus immobilizing, soluble dyes in bydrophilic polymericcolloids such as gelatin which are commonly employed as the film-formingcolloids of photographic materials is commonly accomplished by causingthe dyes to enter into a salt-forming reaction with 1) ionic groups inthe principal film-forming colloid, (2) ionic groups in a compatiblepolymer admixed in minor proportion with the colloid, or (3) ionicgroups in nonpolymeric compounds admixed with a colloid.

A wide variety of protective colloids can be used as vehicles for themordanting compounds. Suitable protective colloids such as hydrophilicpolymers as gelatin and its water soluble derivatives; otherproteinaceous materials which are water permeable, such as polyvinylalcohol and its water soluble derivatives, including copolymers thereof:water soluble vinyl polymers such as polyacrylamide, imidizedpolyacrylamide, etc.; colloidal albumin; water soluble cellulosederivatives such as ethanolamine and cellulose acetate; and relatedwater soluble film-forming hydrophilic polymers that form waterpermeable coatings. If the organic acidic mordanting composition is ahydrophilic organic colloid, an excess of this material over thatutilized to form a salt with the dyes can be used as a protectivecolloid for the dispersed salt. Mixtures of two or more colloids can beutilized. Gelatin is a preferred colloid.

In one embodiment a mordant salt is uniformly dispersed in a hydrophilicpolymer as finely divided particles that are generally less than about30 microns in diameter and preferably less than about 10 microns indiameter.

In another embodiment, the mordanting compound is dispersed in asuitable solvent. Typical low boiling or water soluble organic solventsthat can be utilized in preparing a mordant dispersion include:

(1) substantially water insoluble low boiling solvents such as ethyl andbutyl acetates, ethyl propionate, butyl alcohol, ethyl formate,nitroethane, chloroform, etc.

(2) water soluble solvents such as methyl isobutyl ketone, fi-ethoxyethyl acetate, fl-butoxy-B-ethoxy ethyl acetate, tetrahydrofurfuryladipate, diethylene glycol monoacetate, B-methoxymethyl acetate,acetonyl acetone, diacetone alcohol, diethylene glycol monomethyl ether,ethylene glycol, dipropylene glycol, acetone, ethanol, acetonitrile,dimethylformamide, dioxane, etc.

The low-boiling or water-soluble solvent can be removed from thedispersion, for example, by air drying a chilled, noodled dispersion, orby continuous water Washing.

Likewise, high-boiling, water-immiscible, organic liquids having aboiling point above about C. can be utilized in the mordant dispersionsystem. Any of the high-boiling, water-immiscible solvents described onpage 2, column 2, and page 3, column 1, of US. Patent 2,322,027, issuedJune 15, 1943, can be used. Particularly useful solvents are organiccarboxylic acid esters and organic phosphate esters. Typical solventsinclude di-n-butyl-phthalate, benzyl phthalate, ethyl benzylmalonate,tetrahydrofurfuryl succinate, triphenyl phosphate, tri-o-cresylphosphate, diphenyl mono-p-tert-butylphenyl phosphate, monophenyldi-ochlorophenyl phosphate, tri-tert-butylphenyl phosphate,2,4-di-n-amylphenol, and the like.

Precipitating agents which are particularly useful (for use in thereceiving sheet for use in a black and white diffusion transfer processinclude nuclei which are useful as precipitating agents with a silverhalide complex, including all of those which are commonly useful in thediffusion transfer process. The particular nuclei employed includesilver precipitating agents known in the art such as sulfides,selenides, polysulfides, polyselenides, heavy metals, thiourea, stannoushalides, heavy metal salts, fogged silver halide, Carey Lea silver, andcomplex salts of heavy metals with a compound such as thioaceta mide,dithiooxamide and dithiobiuret. As examples of suitable silverprecipitating agents and of image-receiving elements containing suchsilver precipitating agents, reference may be made to US. Pat.2,698,237, 2,698,238 and 2,698,245 issued to Edwin H. Land on Dec. 28,1954, US. Pat. 2,774,667 issued to Edwin H. Land and Meroe M. Morse onDec. 18, 1956, US. Pat. 2,823,122 issued to Edwin H. Land on Feb. 11,1958, US. Pat. 3,396,018 issued to Beavers et al. Aug. 6, 1968, and alsoUS. Pat. 3,369,901 issued to Fogg et al. Feb. 20, 1968. The noblemetals, silver, gold, platinum, palladium, etc., in the colloidal formare particularly useful.

Noble metal nuclei are particularly active and useful when formed byreducing a noble metal salt using a borohydride or hypophosphite in thepresence of a colloid as described in Rasch US. patent application Ser.No. 796,- 552, filed Feb. 4, 1969, now Patent No. 3,647,440, patentedMar. 7, 1972. The metal nuclei are prepared in the presence of aproteinaceous colloid such as gelatin and coated on the receiving sheet.The same or a different colloid may be added if desired. It will beappreciated that the coating composition generally contains not onlynuclei, but also reaction products which are obtained from reducing themetal salt. Accordingly, it is within the scope of our invention toinclude in the receiving layer the reaction by-products which areobtained during the reducing operation.

The amount of colloid used in preparing the above active noble metalnuclei can be varied depending upon the particular colloid, reducingagent, ratio of proportions, etc. Typically about 0.5% to about 20% byweight based on the total reaction mixture of colloid is used,preferably from about 1% to about 10%.

In a particularly useful embodiment, 30 to 80 micrograms per square footof active palladium nuclei in 80 mg. of colloid (solids basis) is coatedper square [foot of support. Suitalble concentrations on the receivingsheets of active noble metal nuclei as disclosed above can be about 1 toabout 500 micrograms per square foot. Other silver precipitants can becoated in a concentration of up to mg./ft.

Various colloids can be used as dispersing agents or as binders for theprecipitating agents in the receiving layer. Any suitable colloids canbe used. Particularly useful colloids are hydrophilic colloids which areused for binders in silver halide emulsions. Advantageously, they arecoated in a range of about 5-5000 mgjftfi. Included among suit ablecolloids are gelatin, preferably coated at a level in the range of about7-100 mg./ft. polymeric latices such ascopoly(2-chloroethyl-methacrylate-acrylic acid) preferably coated in therange of 15-350 mg./ft. a polymeric vehicle containing two components(1) polyvinyl alcohol, and (2) interpolymer of n-butylacrylate,Z-acryloyloxypropane-l-sulfonic acid, sodium salt and2-acetoacetoxyethyl methacrylate, in a preferred range of about 10-300mg./ft.

It will also be appreciated that the precipitating agents can be formedin situ or can be applied by precipitating or evaporating a suitableprecipitating agent on the surface.

Toning agents are generally present during the diffusion transfer step.For example, various toning agents can be in the processing solution oreven, in some instances, contained in the silver halide emulsion. Toningagents which can be included for improving the tone of the image to makethe tone blacker or more blue-black include sulfur compounds such as2-mercaptothiazoline, 2- amino S-mercapto-1,3,4-thiadiazole,Z-thiononimidazolidene, Z-mercapto-S-methyloxazoline and2-thionoimidazoline. It will be appreciated that these toners can beused either alone or in conjunction with other toning agents. They areparticularly useful in a range of 0.01 to 3.0

mg./ft. either in the receiving layer or coated in a layer on top Oifthe image layer. Other toning agents which may be used include selenotetrazoles, the S-mercaptotetrazoles of Abbott et al., US. Pat.3,295,971 and Weyde, US. Pat. 2,699,393. Still other toning agents aredisclosed in Tregillus et al. US. Pat. 3,017,270.

The receiving layers of our invention may also have therein particlessuch as silica, bentonite, diatomaceous earth such as kieselguhr,powdered glass and fullers earth. In addition, colloids and colloidalparticles of metal oxides such as titanium dioxide, colloidal alumina,coarse aluminum oxide, zirconium oxide and the like may be used with thenuclei in the receiving layers.

In carrying out the diffusion transfer process, conventionally a silverhalide emulsion is exposed to a light image after which it is contactedwith a silver halide developing agent containing a silver halidecomplexing agent. The exposed emulsion is developed in the light struckareas and the unexposed silver halide is complexed with the silverhalide complexing agent after which the emulsion is contacted against areceiving sheet and the complex silver halide diffuses imagewise to thereceiving sheet containing a silver precipitant.

In some instances it may be desirable to treat the receiving sheet inorder to improve the stability of the sheet, particularly with regard tothe silver image thereon. A simple stabilizing method merely involveswashing the print in order to remove any processing chemicals which mayremain thereon. However, the washing step does not protect the printfrom subsequent chemical reactions with oxygen, hydrogen sulfide, etc.,in the atmosphere, which have an adverse effect on the stability of thesilver image. For these reasons, it has been proposed to coat the printwith a coating composition such as that disclosed in US. Patent2,979,477 comprising a mixture of vinylpyridine polymer and ahydantoin-formaldehyde condensation polymer.

Suitable print coating compositions may also employ a polymeric materialsuch as a methylmethacrylate-methacrylic acid copolymer or thecombination of an acid group or sulfate group containing polymer such ascopoly(methylmethacrylate-methacrylic acid) and a hydantoin-formaldehydecondensation polymer, such as that disclosed in French Patent 1,493,188.A heavy metal salt such as zinc acetate may also advantageously beincorporated in the print coating composition. Further improvement isobtained by incorporating in the coating composition an acid such asacetic acid, propionic acid or the like.

Silver halide developing agents used for initiating development of theexposed sensitive element can be conventional types used for developingfilms or papers with the exception that a silver halide solvent orcomplexing agent such as sodium thiosulfate, sodium thiocyanate, ammoniaor the like is present in the quantity required to form a soluble silvercomplex which difiuses imagewise to the receiving support. Usually, theconcentration of developing agent and/or developing agent precursoremployed is about 3 to about 320 mg. /ft. of support.

Developing agents and/or developing agent precursors can be employed ina viscous processing composition containing a thickener such ascarboxymethyl cellulose or hydroxyethyl cellulose. A typical developercomposition is disclosed in US. Patent 3,120,795 of Land et al., issuedFeb. 11, 1964.

Developing agents and/or developing agent precursors can be employedalone or in combination with each other, as well as with auxiliarydeveloping agents. Suitable silver halide developing agents anddeveloping agent precursors which can be employed include, for example,polyhydroxybenzenes, alkyl substituted hydroquinones, as exemplified byt-butyl hydroquinone, methyl hydroquinone and 2,5 dimethylhydroquinone,catechol and pyrogallol; chloro substituted hydroquinones such aschlorohydroquinone or dichlorohydroquinone; alkoxy substitutedhydroquinones such as methoxy hydroquinone or ethoxy hydroquinone;aminophenol developing agents, such as 2,4- diaminophenols andmethylaminophenols. These include, for example, 2,4-diaminopheno1developing agents which cantain a group in the 6 position, and relatedamino developing agents, e.g.:

6-methyl-2,4-diaminophenol 6-methoxy-2,4-diaminophenol6-ethyl-2,4-diaminophenol 6-phenyl-2,4diaminophenol 6-paratolyl-2,4diaminophenol 6-chloro-2,4-diaminophenol6-morpholinomethyl-2,4-diaminophenol 6-piperidino-2,4-diaminophenol3,6-dimethyl-2,4-diaminophenol 6-phenoxy-2,4-diaminophenol2-methoxy-4-arnino-5-methyl phenol 4-aminocatechol 4-aminoresorcinol2,4-diaminoresorcinol methyl-3,4-diaminophenol methoxy-3,4-diaminophenolmethyl-2,5-diaminophenol methoxy-2,5-diaminophenol methyl-1,2,4-triaminobenzene methoxy-1,2,4-triamino benzene p-hydroxyphenyl hydrazinep-hydroxyphenyl hydroxylamine The aminophenol developing agents can beemployed as an acid salt, such as a hydrochloride or sulfate salt.

Other silver halide developing agents include ascorbic acid, ascorbicacid derivatives, ascorbic acid ketals, such as those described in US.Patent 3,337,342 of Green issued Aug. 22, 1967; hydroxylamines such asN,N-di(2- ethoxyethyl)-hydroxylamine; 3-pyrazolidone developing agentssuch as 1-phenyl-3-pyrazolidone, including those described in KodakBritish Patent 930,572, published July 3, 1963; and acyl derivatives ofp-aminophenol such as described in Kodak British Patent 1,045,303,published Oct. 12, 1966; pyrimidine developing agents, such as 4-amino-6,6-dihydroxy-2-methyl pyrimidine; and aminoethyl hydroquinonesilver halide developing agents, such as 2-methyl-S-pyrrolidinomethylhydroquinone, 2-methyls-rnorpholinomethyl hydroquinone, and2-methyl-5-piperidinomethyl hydroquinone. The aminomethyl hydroquinonesilver halide developing agents are especially suitable incorporated inthe negative photographic element.

Another suitable silver halide developing agent which can be used in thepractice of the invention is a reductone silver halide developing agent,especially an anhydro dihydro amino hexose reductone silver halidedeveloping agent, such as anhydro dihydro piperidino hexose reductone,anhydro dihydro pyrrolidino hexose reductone, and/or anhydro dihydromorpholino hexose reductone.

The described reductone silver halide developing agents can be preparedas described in US. Patent 2,936,308 of Hodge, issued May 10, 1960, andin an article by F. Weygand et al., Tetrahedron, volume 6, pages 123-138(1959). Typically the described anhydro dihydro amino hexose reductonecompounds are prepared from the corresponding anhydro amino hexosereductones by hydrogenation in the presence of a suitable hydrogenationcatalyst, such as Raney nickel catalyst. The reductone silver halidedeveloping agent can be employed in various locations in the ditfusiontransfer system, but is especially suitable in the processingcomposition. These can be used alone or in combinations of developingagents. These developing agents provide little or no stain and improvedstability.

Lactone derivative silver halide developing agents which have theproperty of forming a lactone silver halide developing agent precursorunder neutral and acid conditions are particularly useful. Typicallactone derivatives are described in copending US applications Ser. Nos.764,358 and 764,301, filed Oct. 1, 1968 now Pat. No. 3,615,521, patentedOct. 26, 1971, and Pat. No. 3,615,439, patented Oct. 26, 1971,respectively, both entitled, Photographic Compositions and Processes, inthe name of Oftedahl. The particular suitable lactone derivativesprovide desired developing activity and reduction of stain withoutadversely aifecting desired maximum density, minimum density,photographic speed and other desired sensitometric properties. Suitablelactone derivative developing agents include those which under neutral,slightly alkaline or acid conditions, i.e., when the pH is lowered to alevel of about 9 or lower, i.e., about 2 to about 9, do not havesignificant developing activity, if any, due to formation of adeveloping agent precursor.

Silver halide emulsions employed with receiving layers and elements ofthis invention can contain incorporated addenda, including chemicalsensitizing and spectral sensitizing agents, coating agents,antifoggants and the like. They can also contain processing agents suchas silver halide developing agents and/or developing agent precursors.Of course, the processing agents can be incorporated in a layer adjacentto the silver halide emulsion if desired.

The photographic emulsions employed can also be X-ray or othernon-spectrally sensitized emulsions or they can contain spectralsensitizing dyes such as described in US. Patents 2,526,632 of Brookeret al., issued Oct. 24, 1950, and 2,503,776 of Sprague, issued Apr. 11,1950. Spectral sensitizers which can be used include cyanines,merocyanines, styryls and hemicyanines.

The photographic emulsions can contain various photographic addenda,particularly those known to be beneficial in photographic compositions.Various addenda and concentrations to be employed can be determined bythose skilled in the art. Suitable photographic addenda includehardeners, e.g., those set forth in British Patent 974,317; bufferswhich maintain the desired developing activtiy and/ or pH level; coatingaids; plasticizers, speed increasing addenda, such as amines, quaternaryammonium salts, sulfonium salts and alkylene oxide polymers; and variousstabilizing agents, such as sodium sulfite. The photographic silver saltemulsions can be chemically sensitized with compounds of the sulfurgroup such as sulfur, selenium and tellurium sensitizers, noble metalsalts such as gold, or reduction sensitized with reducing agents orcombinations of such materials.

Various photographic silver salts can be used in the practice of theinvention. These include photographic silver halides such as silveriodide, silver bromide, silver chloride, as well as mixed halides suchas silver bromoiodide, silver chloroiodide, silver chlorobromide andsilver bromochloroiodide. Photographic silver salts which are not silverhalides can also be employed such as silver salts of certain organicacids, silver-dye salts or complexes, etc.

The photographic silver salts are typically contained in an emulsionlayer comprising any binding materials suitable for photographicpurposes. These include natural and synthetic binding materialsgenerally employed for this purpose, for example gelatin, colloidalalbumin, watersoluble vinyl polymers, mono and polysaccharides,cellulose derivatives, proteins, water-soluble polyacrylamides,

polyvinyl pyrrolidone and the like, as well as mixtures of such bindingagents. The elements can also contain releasing layers and/or antistaticlayers (i.e., conducting layers).

Stripping agents can be used either on the surface of the silver halideemulsion layer, on the receiving layer containing the nuclei, or can becontained in the developing or processing solutions. When added to theprocessing solution in concentrations of about 3% to about 10% byweight, the stripping agents prevent the processing solution fromsticking to the receiver. Suitable stripping agents normally are usedwhich have a composition different from the binder used in the silverhalide emulsion. Typical stripping agents include alkali permeablepolysaccharides such as, for example, carboxymethyl cellulose orhydroxyethyl cellulose, 4,4dihydroxybiphenol, glucose, sucrose, sorbitol(hexahydric alcohol C H (OH) inositol (hexahydroxy-cyclohexane C H (OH)-2H O), resorcinol, phytic acid sodium salt, thixcin, a castor beanproduct (zinc oxide, and finely divided polyethylene. These coatings arerelatively thin having a preferred coverage of about 6.0 mg./ft.However, a useful range may be from 1.0 mg. to 1.0 g./ft.

Release agents can be used either on the surface of the silver halideemulsion layer, on the receiving layer containing the nuclei, or can becontained in the developing or processing solutions.

In one embodiment a resinous mixed ester lactone release agent isemployed as a binder for the silver precipitant in an amount of 1mg./ft. to about 1 g./ft. It will be appreciated that when smalleramounts are used, that the resinous material can be combined with asuitable colloid such as a proteinaceous material. For example, theresinous material might be coated at a range of 1 mg./ft. and becombined with gelatin in an amount of 13 mg./ft. At the upper end of therange, the resinous material of 1 g./ft. can be used withoutincorporating any other colloidal material.

When used as an overcoat over a binder layer containing a silverprecipitant, the materials may be used in a range of 1.0 to 20.0 mg./ft.the preferred coverage being about 4.0 mg./ft. to about 8.0 mg./ft.

Resinous lactones of the type described herein and the process of makingthese lactones are described in U.S. Patents 3,169,946; 3,007,901;3,206,312; 3,260,706; 2,306,- 071; and 3,102,028. Their use as releaseagents is described in Checkhak U.S. Patent application Ser. No. 2,965,filed Jan. 14, 1970, now abandoned.

In one embodiment a resinous lactone release agent is mixed with asilver precipitant, such as colloidal metal nuclei, a proteinaceousbinder such as gelatin, a polyvinyl quaternary salt such aspoly(1-methyl-4-vinylpyridinium methosulfate) and potassium iodide. Themixture is coated on a support of this invention and after drying can beused as a receiving sheet in a diffusion transfer process.

In the event that a proteinaceous binder is employed with a silverprecipitating agent, gelatin is preferred, but other proteins such ascasein, zein, albumin, etc., may be used. However, any suitable colloidor colloids may be used, including both Water-soluble polymers andwater-insoluble polymers. A latex or hydrosol may advantageous- 1y beemployed if the polymer is insoluble in Water. Polymers which areparticularly useful are water soluble polyvinyl quaternary salts, asdescribed in Van Hoff et a1. U.S. Patent 3,174,858, issued Mar. 23,1965. These Water soluble basic polymeric quaternary salts have apolyvinyl chain having 2 to 10,000 monomeric units, each monomeric unitof which is linked directly to a five or six membered heterocyclicnucleus containing as heteroatoms only nitrogen atoms, one of whichhetero-nitrogen atoms being a quaternary nitrogen atom.

In one embodiment, the polymer has the following structure:

in which n is an integer from 2 to 10,000 and X is any suitable anionsuch as CH SO para toluene sulfonate iodide, etc. R represents H, analkyl group having 1 to 10 carbon atoms such as, for example, methyl,ethyl, propyl, butyl, etc., halogen, N0 NH aralkyl, aryl, etc. R isselected from the same group as R, but can be a different group than R.It will be appreciated, of course, that the heterocyclic nucleus cancontain additional nitrogen atoms and that the ring may be substitutedwith other groups. The substituents can be the same or different.

Typical polymeric materials include poly 1,Z-dimethyl-S-vinylpyridiniummethylsulfate) polyl ,4-vinylpyridiniummethylsulfate) poly(1-methyl-2-vinylpyridinium iodide) poly (1-methy1-2-vinylpyridiniummethylsulfate), poly( 1-methyl-4-vinyl-pyridinium iodide),

poly 1-methyl-4-vinylpyridinium methylsulfate poly(1-viny1-3-methylimidazolium iodide) and poly(1-vinyl-3-methyl imidazoliummethylsulfate).

In a particularly useful coating composition is employed from 0.1 tomg./ft. preferably 0.2 to about 5 mg./ft. In a typical embodiment, 30mg. of the polyvinyl polymer are used for 1 g. of gel in the receivinglayer.

An alkali or alkali metal iodide such as, e.g. ammonium, sodium,potassium, lithium iodide, etc., can be present in the receiver in anamount of about 0.1 to about 20 mg./ft.'-, preferably 0.5 to about 10mg./ft. An improvement in cold tone in certain receiving layers which isobtained as a result of iodide is particularly unexpected, sincepotassium iodide contained in the processing solution in an amount ofabout 1.6 g. of potassium iodide per liter and which is spread at acoverage of about 3.5 mL/ft. fails to give a satisfactory tone. Also,iodide present in the negative in an amount of about 10 mg./ft. alsofails to have an effect on the tone.

The addition of a silver salt or complex such as, e.g. silver nitrate,to certain receiving sheets further improves the tone as does theaddition of diffusion transfer toners. Any silver salt or complex can beused, including both organic and inorganic silver compounds. A typicalorganic silver complex is, for example, silver dipyridyl nitrate. Othersilver salts and complexes which are included are described in Gilman etal., U.S. Patent No. 3,446,619. Still other silver salts ofmercaptotetrazoles and mercaptotriazoles and related heterocyclicmercapto compounds are described in U.S. Patent No. 2,432,864. However,silver nitrate is preferred. The silver compound can be used in anamount of about 0.01 to about 10 mg./ft. preferably 0.05 to about 5mg./ft.

Various toners can be used by incorporating the toner in the receivedsheet. Particularly useful toners are those disclosed for use withcertain quaternary salts in Tregillus and Rasch U.S. Patent No.3,017,270, issued Jan. 16, 1962.

In a preferred embodiment, the toner used is a seleno tetrazole,including seleno tetrazoles substituted by aliphatic residues, as forexample, 1-allyl-5-seleno-1,2,3,4- tetrazole, seleno tetrazolessubstituted by aromatic or heterocyclic residues having 1-12 carbonatoms, as for example, l-phenyl-S-seleno 1,2,3,4 tetrazole, etc. Thetoners can be used in the amount of about 0.005 to about 5.0 mg./ft.preferably 0.01 to about 1 mg/ftF. These toners may be contained in adeveloper or activator solution.. A particularly useful combinationemploys phenyl mercaptotetrazole and potassium iodide in a developer oractivator solution.

Coating solutions which contain addenda other than a silver precipitantare also useful in preparing receiving layers. In addition to variouscomponents contained in the coating composition according to thisinvention, toners, surfactants, coating aids, developing agents, silverhalide solvents, etc., may be added to improve the image quality in thereceiving sheet.

Particularly useful surfactants and spreading agents in receivercoatings include saponin, lauryl alcohol sulfate, p-tert octyl phenoxyethoxy ethyl sodium sulfonate, etc.

Developers, which can be used in a solvent transfer system such asdescribed in U.S. Patent 2,543,181 of Land issued Feb. 27, 1951, cancontain release agents. When added to the developer in concentrations ofabout 3 to about by weight, the release agents aid in preventing thedeveloper from sticking to the receiver. Suitable release agentsinclude, for example:

4,4'-dihydroxybiphenyl glucose 5 sucrose sorbitol (hexahydric alcohol CH (OI-I) inositol (hexahydroxy-cyclohexane C H (OH) -2H O) resorcinolphytic acid sodium salt thixcin (a castor bean product) zinc oxide, and

finely divided polyethylene.

It willalso be appreciated that a lithographic printing 5 plate can beprepared using the photographic element of this invention. After theimage is formed in the receiving layer, it can be treated by methodsknown in the art such as by treatment with a thiol or similar sulfurcontaining compound in order to improve the ink-water differentialbetween the image areas and the non-image areas of the receiving layer.Subsequently, the element can be used as a printing plate by wetting andinking in the typical lithographic process. 7

In the attached drawing is given a structural configurationof the layersemployed in a preferred structure for the receiving sheet of thisinvention.

FIG. l'illustrates a black and white receiving sheet in which paperstock 3 has coatings 2 and 1 of black polyethylene 2 and whitepolyethylene 1 respectively on the back side of the paper 3. On the faceside of paper stock 3 are coated a baryta layer 4 and over the barytalayer a layer of clear polyethylene 5. The clear polyethylene 5 issubbed with a gelatin-cellulose nitrate subbing 6 over which is coated alayer 7 of cellulose triacetate plus a brightener. On this layer 7 issolvent coated a gelatin subbing' 8 and finally the gelatin nuclei layer9.

In FIG. 2 the structure is the same as FIG. 1 except that a gelatinmordant layer 10 is coated as the top layer instead of the gelatinnuclei layer 9. 40

The following examples are included for a further understanding of theinvention:

EXAMPLE 1 Receiving elements are prepared having a nucleated layercomprising a gelatin binder containing finely divided palladium nuclei.In each instance, white polyethylene coated paper is employed in whichthe polyethylene surface has been electron bombarded to a contact anglebelow 70 measured with water to improve the adhesion. In Coating A thenucleated layer is coated directly on the polyethylene coated paper. Incoatings B and C the nucleated layers are coated over a plastic layer ofcellulose triacetate of about 10 grams per square meter which is locatedbetween the nucleated layer and the polyethylene surface.

In coating C, a thin subbing layer of a mixture of gelatin and cellulosenitrate of thefollowing formula is applied to the polyethylene supportbefore coating with cellulose triacetate. In coatings B and C a thinsubbing layer of the same composition is coated over the triacetatelayer before coating with the nucleated layer.

Percent Gelatin 1.25 Cellulose nitrate 0.6 Glacial acetic acid 1.0Acetone 60.0 Water 3.0 Ethylene dichloride 5.0 Methanol 29.15

To this formula is added 1.5 percent of the weight of gelatin ofhydrated chromium chloride as a hardener. Abrasion resistance measuredas scratch resistance of the nucleated surface is measured on theprocessed samples using a Taber Scratch Tester Model 503. Thisinstrument applies an adjustable load to a 15-mil radius sapphire styluswhich is placed on the material to be tested. The material is movedbeneath the load stylus at a constant speed and the load is adjusteduntil the stylus scratches through the nucleated coating to thesubstrate. This point is visually observed by noting when the whitesubstrate is apparent in the scratched area. Testing is carried outwithin about one hour after the receiver and negative are stripped apartafter processing in a diffusion transfer system in which an exposedsilver halide emulsion is developed in the presence of a silver halidesolvent and in contact with the nucleated layer.

The following values are obtained in testing the above coatings.

Scratch value,

Coating Support deserlption grams A... Polyethylene 5 B-.. Triacetateover unsubbed polyethylene 17 C Trlacetate over subbed polyethylene 500EXAMPLE 2 Receiving elements are prepared as in coating B, Example 1.The following results are obtained by testing as in Example' l.

Scratch value,

Polymer Base grams Cellulose triacetate Polyethylene coated paper-. 176Cellulose acetate butyrate .do

Receiver stability with all coatings is good. Other polymer coatingsemployed over polyethylene in place of cellulose triacetate includepolystyrene, polyvinyl butyral, and a styreneacrylonitrile copolymer.The triacetate has superior characteristics, such as adhesion, curl,toughness and flexibility.

EXAMPLE 3 EXAMPLE 4 Example 1 is repeated except that the polymer coatcomprises a 1:1 weight ratio of carboxylated polyester and cellulosetriacetate which is coated out of a solvent solution of methylenechloride and methyl alcohol in a weight ratio of 9:1. The polymercoating is applied to the electron bombarded polyethylene coated paperwithout a subbing but a cellulose nitrate sub as described in Example 1is coated over the polymer coating prior to coatwith the nucleatedlayer. Average scratch value is EXAMPLE 5 A receiving sheet for use inobtaining an image by the dye diffusion transfer process is prepared byusing electron bombarded polyethylene coated paper as in Example 1. Overelectron bombarded polyethylene is coated a sub as described inExample 1. Coatings are also made employing subs as described in Example3. Over each of these subbed polyethylene coated paper supports arecoated polymer layers including those described in Examples 1, 2 and 4.Over the polymer layer is coated a subbing over which is then coated adispersion containing a dye mordanting composition comprising octadecyltri-n-butyl ammonium bromide as described in Example 1 of U.S. Patent3,271,147. The receiving sheets are used in the image transfer colorprocesses as is described in Example 6 of U.S. Patent 3,271,147.Subsequent testing for abrasion indicates that the abrasion values areat least 500 when tested as described in Example 1. The use of othermordant compounds as described in the above patent also result insatisfactory abrasion resistant receiving sheets.

EXAMPLE 6 Scratch abrasion value,

Support Dmnx. grams Cellulose acetate butyrate, 8 mil 1. 45 1, 000Cellulose acetate butyrate. 16 mil 1. 45 300 The invention has beendescribed in detail with particular reference to preferred embodimentsthereof, but it will be understood that variations and modifications canbe effected within the spirit and scope of the invention.

What is claimed is:

1. A receiving sheet comprising a polyolefin surface over which iscoated a cellulose'triacetate layer and over said cellulose triacetatelayer is coated an image receiving layer containing palladium nuclei.

2. An element of claim 1 in which said polyolefin surface has a contactangle of about 40 to about measured with water, prior to coating withthe cellulose layer.

3. A receiving sheet of claim 1 in which said polyolefin ispolyethylene.

4. An element of claim 1 in which said cellulose layer contains abrightener. i

5. An element of claim 1 in which a gelatin-cellulose nitrate sub isemployed over the said polyolefin surface.

6. An element of claim 1 comprising a paper support having a barytalayer on said paper and having said polyolefin over said baryta layer.

7. An element of claim 1 comprising a paper support having thereon saidpolyolefin.

References Cited UNITED STATES PATENTS 3,265,505 8/1966 Yudelson 96-763,161,519 12/1964 Alsup 1l7--155X 3,212,897 10/1965 Secrist 9 6-853,295,979 1/1967 Secrist et a1. 96-76 WILLIAM D. MARTIN, PrimaryExaminer M. R. LUSIGNAN, Assistant Examiner U.S. C1. X.R.

117-34, 73, 76 F, 76 P; 96-76 R, 87 R

